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Study on Bearing Capacity of Tank Foundation with Alternatively Arranged Vortex-Compression Nodular Piles

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Study on Bearing Capacity of Tank Foundation with Alternatively Arranged Vortex-Compression Nodular Piles energies Article Study on Bearing Capacity of Tank Foundation with Alternatively Arranged Vortex-Compression Nodular Piles Chun-Bao Li *, Gao-Jie Li, Ran-Gang Yu, Jing Li and Xiao-Song Ma Department of Civil Engineering, China University of Petroleum (East China), Qingdao 266580, China; [email protected] (G.-J.L.); [email protected] (R.-G.Y.); [email protected] (J.L.); [email protected] (X.-S.M.) * Correspondence: [email protected]; Tel.: +86-532-8698-1820 Received: 8 September 2020; Accepted: 8 October 2020; Published: 11 October 2020 Abstract: Types of tapered piles are widely applied in tank foundation consolidation, but their inherent deficiencies in design and construction limit their further promotion. Vortex compression pile is a novel nodular pile. Compared with the traditional equal-section pile, vortex compression nodular pile is featured by stronger bearing capacity and slighter settlement. In this paper, the model test results showed that vortex compression nodular pile can greatly improve the bearing capacity and reduce the settlement. Through the finite element software ABAQUS analysis the bearing characteristics of equal-section pile foundation and vortex-compression nodular pile foundation were compared. The three-dimensional solid model was established by ABAQUS finite element software. The impact of cushion modulus, cushion thickness, vertical load, pile modulus, soil modulus around the pile on the bearing capacity of the vortex-compression nodular pile foundation were studied. Keywords: vortex-compression nodular pile; composite foundation; bearing capacity; tank foundation 1. Introduction In China, most storage tanks in oil and gas reserve projects, with a volume larger than 105 m3, are built on soft foundation area [1]. These tanks are featured by large volume and heavy load, putting strict requirements on the bearing capacity of tank foundation and the control of uneven settlement [2]. At present, because of improper site selection, poor foundation consolidation, and improper foundation structure form, uneven settlement of tank foundation has become outstanding, which results in tank body tilt, floating roof displacement and sticking, tank body distortion, and other related problems [3,4]. Therefore, how to strengthen the foundation, improve the bearing capacity, and mitigate the uneven settlement while saving resources have been the focuses of civil engineering workers [5]. Through the analysis of compaction test in specific projects, Lin P. concluded that gravel pile reinforcement can improve the bearing capacity of tank foundation by compacting soil, which is simple in construction, mature in technology, and can save a lot of cement and steel [6]. Jia J carried out static load test, dynamic penetration test, and standard penetration test on gravel pile composite foundation. They concluded that the modulus of cushion under flexible foundation should fall in the range of 80–200 MPa and reported critical pile length for certain load capacity and strain. They also suggested that appropriate replacement rate can give full play to the load capacity of soil [7]. Combined with the specific engineering geology and trial pile result data of the Cement Fly-ash Gravel(CFG) pile composite foundation of Dongying storage tank, Dong H. obtained the settlement of the foundation under circular uniform load and the load transfer law of the pile body [8]. Song X. simulated the CFG pile by ADINA finite element software. He found that the force mode of side pile and middle pile are not exactly the Energies 2020, 13, 5273; doi:10.3390/en13205273 www.mdpi.com/journal/energies Energies 2020, 13, x FOR PEER REVIEW 2 of 18 of the foundation under circular uniform load and the load transfer law of the pile body [8]. Song X. simulated the CFG pile by ADINA finite element software. He found that the force mode of side pile and middle pile are not exactly the same, so their load transfer law is also different. Besides, the pile- soil stress ratio is directly proportional to the cushion modulus and increasing the cushion thickness Energies 2020, 13, x FOR PEER REVIEW 2 of 18 or reducing the cushion modulus can mitigate the stress concentration [9]. Li P. simulated the Energies 2020 13 vibroflotationof the foundation, g,ravel 5273 under pile circularby PLAXIS uniform finite load elementand the load software transfer, tlawhe ofdifferential the pile body settlement [8]. Song2 of X 18under. differentsimulated pile length,the CFG replacem pile by ADINAent rate, finite pile element diameter software and pile. He foundspacing that are the studied. force mode He concludedof side pile that the differentialsame,and middle so their pilesettlemen load are transfer nott exactlyis lawnegatively is the also same di ffcorrelatederent., so the Besides,ir load with transfer the the pile-soil replacement law stressis also ratio different rate is,directly and. Besides, pile proportional diameter the pile- [10]. Throughtosoil the stress cushionnumerical ratio modulusis directlysimulation, and proportional increasing Liu H. to the theconcluded cushion cushion thickness modulusthat the or and reducinginfluence increasing the of cushionthe tank cushion modulusgroup thickness effect can on foundationmitigateor reducing settlement the stressthe cushion concentration is negatively modulus [9 correlated ].can Li P.mitigate simulated with the the thestress load vibroflotation concentration on the tank gravel foundation[9]. pile Li byP. simulated PLAXIS [11]. finite the elementvInibroflotation 2014, software, Li C. getravel theal. proposed dipffileerential by P theLAXIS settlement vortex finite undercompression element different software nodular pile length,, the pile, replacementdifferential developed rate,settlement the pile equipment diameter under and toolsanddifferent for pile construction, spacingpile length, are secured studied.replacem Heentnational concludedrate, pile invention diameter that the patent, and diff erentialpile a spacingnd settlementput areforward studied. is negatively a Henew concluded method correlated thatfor tank foundationwiththe differential the consolidation, replacement settlemen rate, tthat is and negatively is, pile the diameter vortex correlated c [ompression10]. Throughwith the nodularreplacement numerical pile simulation, rate foundation, and pile Liu diameterwith H. concluded alternatively [10]. Through numerical simulation, Liu H. concluded that the influence of tank group effect on arrangedthat the nodular influence parts of tank [12– group14]. Through effect on foundationindoor model settlement tests, the is negatively load transfer correlated mechanism with the of load vortex- foundation settlement is negatively correlated with the load on the tank foundation [11]. compressionon the tank nodular foundation pile [and11]. the distribution law of side friction along the pile under different loads InIn 2014, 2014, Li Li C. C. et et al. al. proposed proposed the the vortex vortex compression compression nodular nodular pile, pile, developed developed the theequipment equipment and are studied. This paper focuses on the vertical bearing capacity and the settlement behavior of vortex- andtools toolsfor construction, for construction, secured secured national national invention invention patent,patent, and put and forward put forward a new method a new methodfor tank compression nodular pile as well as the development law of the plastic failure zone of the soil around forfoundation tank foundation consolidation, consolidation, that is, the that vortex is, thecompression vortex compression nodular pile nodular foundation pile with foundation alternatively with the nodularalternativelyarranged partnodular arrangeds [15 parts–18] nodular [12. Through–14]. parts Through [the12– 14numerical indoor]. Through model simulation indoor tests, model the loadof tests, ABAQUS transfer the load mechanism software, transfer mechanism ofthe vortex influence- factorsofcompression vortex-compressionof pile foundation nodular pile nodular with and thealternatively pile distribution and the arranged distributionlaw of side nodular friction law of along sideparts frictionthe are pile analyzed. alongunderthe different The pile foundat under loads ion settlementdiareff erentstudied. and loads Thpileis are -papersoil studied. stress focus Thisesratio on paper theunder vertical focuses different bearing on thepile capacity vertical modulus, and bearing the soil settlement capacitymodulus andbehavior around the settlement of pile, vortex cushion- modulus,behaviorcompression cushion of vortex-compression nodular thickness pile asand well load nodularas the are development studied pile as well[19 –law as21] theof. the development plastic failure law zone of the of the plastic soil around failure zonethe nodular of the soilpart arounds [15–18] the. Through nodular partsthe numerical [15–18]. Throughsimulation the of numerical ABAQUS simulation software, the of ABAQUSinfluence 2. Experimentalsoftware,factors of the pile influence Work foundation factors with of pilealternatively foundation arranged with alternatively nodular parts arranged are nodularanalyzed. parts The are foundat analyzed.ion Thesettlement foundation and pile settlement-soil stress and ratio pile-soil under stress different ratio under pile modulus, different pilesoil modulus,modulus soilaround modulus pile, cushion around 2.1. Tpile,modulus,echnical cushion Informationcushion modulus, thickness of cushion Pile and Forming thickness load are andstudied load [19 are–21] studied. [19–21].
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